Method for forming a mask by etching conformal film on patterned ashable hardmask
Methods and apparatuses for multiple patterning using image reversal are provided. The methods may include depositing gap-fill ashable hardmasks using a deposition-etch-ash method to fill gaps in a pattern of a semiconductor substrate and eliminating spacer etching steps using a single-etch planarization method. Such methods may be performed for double patterning, multiple patterning, and two dimensional patterning techniques in semiconductor fabrication.
1. A method of processing a semiconductor substrate, the method comprising:
transferring a pattern from an overlying photoresist to a core amorphous carbon layer;
depositing a conformal film over the patterned core amorphous carbon layer on the semiconductor substrate;
depositing a gap-fill amorphous carbon layer over the conformal film;
planarizing the semiconductor substrate with a process that etches both the conformal film and the gap-fill amorphous carbon layer to remove the conformal film over the core amorphous carbon layer while leaving the conformal film deposited between the core amorphous carbon layer and the gap-fill amorphous carbon layer; and
selectively etching the conformal film to form a mask.
2. The method of claim 1 , wherein the semiconductor substrate is planarized by
flowing oxygen and helium at about 20 sccm and about 200 sccm, respectively;
exposing the semiconductor substrate to an aqueous hydrofluoric acid solution;
flowing CF 4 and Ar at about 5 sccm and about 100 sccm, respectively; and
flowing CHF 3 and CF 4 at about 15 sccm and about 80 sccm, respectively.
3. The method of claim 2 , wherein flowing oxygen and helium occurs for about 30 seconds, flowing CF 4 and Ar occurs for about 10 seconds, and flowing CHF 3 and CF 4 occurs for about 30 seconds.
4. The method of claim 1 , wherein the semiconductor substrate is planarized at a temperature between about 10° C. and about 50° C. and a pressure between about 2 Torr and about 20 Torr.
5. The method of claim 1 , wherein the semiconductor substrate is planarized using chemical mechanical planarization.
6. The method of claim 1 , wherein the gap-fill amorphous carbon layer is deposited by
(a) flowing a hydrocarbon using plasma enhanced chemical vapor deposition until a gap entry width between features in the pattern is reduced,
(b) directionally sputtering ions generated from a plasma to anisotropically etch the semiconductor substrate with a dominant anisotropic axis substantially perpendicular to the semiconductor substrate,
(c) repeating X cycles of (a) and (b), wherein X is a positive integer, and
(d) ashing the semiconductor substrate to remove localized build-up of carbon film on a surface of the semiconductor substrate.
7. The method of claim 6 , wherein the hydrocarbon is methane, acetylene, or propylene.
8. The method of claim 1 , wherein the pattern further comprises features with aspect ratios between about 1:1 and about 5:1.
9. The method of claim 1 , further comprising patterning a target layer with the mask.
10. The method of claim 1 , further comprising:
prior to transferring a pattern from an overlying photoresist to a core amorphous carbon layer, transferring the pattern from an overlying photoresist to a bottom anti-reflective layer and cap layer simultaneously by pulsing power.
11. A method of processing a semiconductor substrate, the method comprising:
transferring a pattern from a overlying first photoresist to a core first amorphous carbon layer in a first dimension;
depositing a first conformal film over the patterned core first amorphous carbon layer on the semiconductor substrate;
depositing a second amorphous carbon layer over the first conformal film;
selectively etching the second amorphous carbon layer and the core first amorphous carbon layer to expose the patterned first conformal film;
etching an underlying etch stop layer using the patterned first conformal film;
depositing a gap-fill third amorphous carbon layer;
depositing and lithographically defining a second photoresist in a second dimension;
depositing a second conformal film over the second patterned photoresist;
selectively etching the second conformal film to expose the second patterned photoresist;
selectively etching the second patterned photoresist;
selectively etching the gap-fill third amorphous carbon layer; and
selectively etching an underlying cap layer to form a two-dimensional mask.
12. The method of claim 11 , further comprising:
depositing and lithographically defining a third photoresist layer on the second amorphous carbon layer to form a block mask; and
selectively etching the second AHM layer using the block mask.
13. The method of claim 11 , wherein depositing the gap-fill third amorphous carbon layer further comprises
(a) flowing a hydrocarbon using plasma enhanced chemical vapor deposition until a gap entry width between features in the pattern is reduced,
(b) anisotropically etching the semiconductor substrate with a dominant anisotropic axis substantially perpendicular to the semiconductor substrate,
(c) repeating X cycles of (a) and (b), wherein X is a positive integer, and
(d) ashing the semiconductor substrate to remove localized build-up of carbon film on the surface.
14. The method of claim 13 , wherein the hydrocarbon is methane, acetylene, or propylene.
15. The method of claim 11 , wherein the second pattern further comprises features with aspect ratios between about 1:1 and about 5:1.
16. The method of claim 11 , further comprising patterning a target layer with the two-dimensional mask.
17. The method of claim 11 , wherein the second conformal film is deposited at a temperature less than about 80° C.